In a pilot study of the petrochemical industry, it was discovered that most of the hazardous and non-hazardous waste steams produced contained high BTU values. Most of these wastes, however, are disposed of in landfills or by incineration. The National Priorities List of Hazardous Waste Sites shows an abundance of sites with relatively high BTU value wastes.
There is an increasing trend for many producers of high heating value wastes to resort to commercially operating cement and lime kilns for ultimate disposal of such waste. The Environmental Protection Agency has already initiated a similar effort in the Fuels Project. This project currently disposes only of liquid wastes with high BTU value. Presently, certain companies provide safe disposal service for combustable liquid waste producers.
Most cement kilns accepting these wastes can use only liquid fuels. The normal criterion for acceptance of waste is that the heating value of the waste exceed 10,000 BTU per pound. Cement kilns come in four basic configurations that represent an evolutionary scale toward increasing energy efficiency. The four types are: wet process, long dry, preheater, and precalcinating. Although cement kilns function as excellent incinerators these kilns burning hazardous wastes have emphasized the resource recovery nature of this practice and operate as industrial furnaces which burn waste for energy and resource recovery.
Cement kilns have huge appetites for fuel and raw materials. A relatively small wet process kiln, for example, may consume forty-three tons dry weight of feed stock, six thousand five hundred gallons of water, and one hundred seventy million BTU to produce thirty tons per hour of clinker. Such apparent inefficiencies can lead to the demise of similar wet kilns in today's energy conscious times. However, the liabilities of this old, wet process kiln can become assets when the kiln is used to co-process wastes. Cement kilns offer the tremendous advantage of being able to utilized many diverse types of wastes for their energy content and/or resource value.
Cement kilns have been established as effective devices for energy recovery while burning liquid waste for fuel. However, there are equally important opportunities for the utilization of other waste products.
In general, industrial wastes contain numerous inorganics, but are low in organics. These are introduced into the cool end of the kiln as components of the slurry. Also, certain waste waters that are low in organics also can be used to displace water in the formation of this slurry. Many metal bearing wastes are also compatible with cement making. Iron and aluminum are normal cement constituents, but other heavy metals also will become bound in the crystalline structure of the clinker. Lead and zinc are eliminated mainly in dust as opposed to clinker when the kiln is fired with halogenated fuels. Halogens can have positive influences in the kiln by removing sodium and potassium, for example. This occurs because the alkaline salts have boiling points lower than the temperature in the burning zone of the kiln. The volatile potassium and sodium salts are condensed in the air stream in cooler regions of the kiln and are removed as kiln dust. Fluroide may enter into the clinkering reaction as a flux and thus serves as a burning aid.
In the past, it has been very difficult to utilize waste solids in cement kilns. Kilns that have tried to burn these wastes have encountered problems with the handling and the feeding of the kilns. It is especially difficult when the solids or sludges contain a high level of organic and hazardous constituents in the wastes. In such situations, the natural vapor emission from such organic and hazardous constituents would prevent their use in the cement kiln. It becomes very difficult to control the migration of pollutants from the fuel product.
It is an object of the present invention to provide a process for the manufacture of a fuel product that allows high BTU waste products to be utilized as a fuel product.
It is another object of the present invention to provide a process that allows commercially operating kilns to receive hazardous and non-hazardous sludges and wastes in solid form.
It is another object of the present invention to provide a process that enhances the cross-linking and microencapsulation of organic constituents within the wastes.
It is still a further object of the present invention to provide a process that enhances the ability to handle and utilize a fuel product.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.